You build it: Hero Rom Upgrade

OK so you downloaded the new ROM version, but you cant find a 68764 (8K Eprom in 24 pin package). Well here is a little conversion you can do to allow you to use a 2764 (8K Eprom in 28 pin package).

 1  tie high (+5)
 2  tie to socket #21
 28 tie to socket #24
 27 tie high (+5)


  24 Pin    28 Pin     Notes
--------------------------
   Vcc 24   26 N/C     OK to pass through 
   A8  23   25 A8      OK to pass through
   A9  22   24 A9      OK to pass through
   A12 21   23 A11     Socket to prom#2, pin to socket #18 
   E   20   22 OE      OK to pass through
   A10 19   21 A10     OK to pass through
   A11 18   20 CE      Socket to prom#23, pin to ground